package com.com.ruanmeng.view;

import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ListAdapter;
import android.widget.ListView;

public class PinnedHeaderListView extends ListView { 
	   public interface PinnedHeaderAdapter { 
		public static final int PINNED_HEADER_GONE = 0; 
		public static final int PINNED_HEADER_VISIBLE = 1; 
		public static final int PINNED_HEADER_PUSHED_UP = 2; 
		int getPinnedHeaderState(int position); 
		void configurePinnedHeader(View header, int position, int alpha); 
		} 
		private static final int MAX_ALPHA = 255; 
		private PinnedHeaderAdapter mAdapter; 
		private View mHeaderView; 
		private boolean mHeaderViewVisible; 
		private int mHeaderViewWidth; 
		private int mHeaderViewHeight; 
		public PinnedHeaderListView(Context context) { 
		super(context); 
		} 
		public PinnedHeaderListView(Context context, AttributeSet attrs) { 
		super(context, attrs); 
		} 
		public PinnedHeaderListView(Context context, AttributeSet attrs, 
		int defStyle) { 
		super(context, attrs, defStyle); 
		} 
		protected void onLayout(boolean changed, int left, int top, int right, int bottom) { 
		super.onLayout(changed, left, top, right, bottom); 
		if (mHeaderView != null) { 
		mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight); 
		configureHeaderView(getFirstVisiblePosition()); 
		} 
		} 
		protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
		super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
		if (mHeaderView != null) { 
		measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec); 
		mHeaderViewWidth = mHeaderView.getMeasuredWidth(); 
		mHeaderViewHeight = mHeaderView.getMeasuredHeight(); 
		} 
		} 
		public void setPinnedHeaderView(View view) { 
		mHeaderView = view; 
		if (mHeaderView != null) { 
		setFadingEdgeLength(0); 
		} 
		requestLayout(); 
		} 
		public void setAdapter(ListAdapter adapter) { 
		super.setAdapter(adapter); 
		mAdapter = (PinnedHeaderAdapter)adapter; 
		} 
		public void configureHeaderView(int position) { 
		if (mHeaderView == null) { 
		return; 
		} 
		int state = mAdapter.getPinnedHeaderState(position); 
		switch (state) { 
		case PinnedHeaderAdapter.PINNED_HEADER_GONE: { 
		mHeaderViewVisible = false; 
		break; 
		} 
		case PinnedHeaderAdapter.PINNED_HEADER_VISIBLE: { 
		mAdapter.configurePinnedHeader(mHeaderView, position, MAX_ALPHA); 
		if (mHeaderView.getTop() != 0) { 
		mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight); 
		} 
		mHeaderViewVisible = true; 
		break; 
		} 
		case PinnedHeaderAdapter.PINNED_HEADER_PUSHED_UP: { 
		View firstView = getChildAt(0); 
		int bottom = firstView.getBottom(); 
		int headerHeight = mHeaderView.getHeight(); 
		int y; 
		int alpha; 
		if (bottom < headerHeight) { 
		y = (bottom - headerHeight); 
		alpha = MAX_ALPHA * (headerHeight + y) / headerHeight; 
		} else { 
		y = 0; 
		alpha = MAX_ALPHA; 
		} 
		mAdapter.configurePinnedHeader(mHeaderView, position, alpha); 
		if (mHeaderView.getTop() != y) { 
		mHeaderView.layout(0, y, mHeaderViewWidth, mHeaderViewHeight 
		+ y); 
		} 
		mHeaderViewVisible = true; 
		break; 
		} 
		} 
		} 
		protected void dispatchDraw(Canvas canvas) { 
		super.dispatchDraw(canvas); 
		if (mHeaderViewVisible) { 
		drawChild(canvas, mHeaderView, getDrawingTime()); 
		} 
		} 
		} 